1. Field of the Invention
The field of the invention relates to electro-optical readers or scanning systems, such as bar code symbol readers, and more particularly to the optical path design in a scanning module for use in applications requiring particularly compact bar code readers.
2. Description of the Related Art
Electro-optical readers, such as bar code symbol readers, are now very common. Typically, a bar code symbol comprises one or more rows of light and dark regions, typically in the form of rectangle. The widths of the dark regions, i.e., the bars and/or the widths of the light regions, i.e., the spaces, between the bars encode information in the symbol.
A bar code symbol reader illuminates the symbol and senses light reflected from the regions of differing light reflectivity to detect the relative widths and spacings of the regions and derive the encoded information. Bar code reading type data input systems improve the efficiency and accuracy of data input for a wide variety of applications. The ease of data input in such systems facilitates more frequent and detailed data input, for example to provide efficient inventories, tracking of work in progress, etc. To achieve these advantages, however, users or employees must be willing to consistently use the readers. The readers therefore must be easy and convenient to operate.
A variety of scanning systems are known. One particularly advantageous type of reader is an optical scanner which scans a beam of light, such as a laser beam, across the symbols. Laser scanner systems and components of the type exemplified by U.S. Pat. Nos. 4,387,297 and 4,760,248 which are owned by the assignee of the instant invention and are incorporated by reference herein have generally been designed to read indicia having parts of different light reflectivity, i.e., bar code symbols, particularly of the Universal Product Code (UPC) type, at a certain working range or reading distance from a hand-held or stationary scanner.
A variety of mirror and motor configurations can be used to move the beam in a desired scanning pattern. For example, U.S. Pat. No. 4,251,798 discloses a rotating polygon having a planar mirror at each side, each mirror tracing a scan line across the symbol. U.S. Pat. Nos. 4,387,297 and 4,409,470 both employ a planar mirror which is repetitively and reciprocally driven in alternate circumferential directions about a drive shaft on which the mirror is mounted. U.S. Pat. No. 4,816,660 discloses a multi-mirror construction composed of a generally concave mirror portion and a generally planar mirror portion. The multi-mirror construction is repetitively reciprocally driven in alternative circumferential directions about a drive shaft on which the multi-mirror construction is mounted. All of the above-mentioned U.S. Patents are incorporated herein by reference.
In electro-optical scanners of the type discussed above, the xe2x80x9cscan engine xe2x80x9d including the laser source, the optics, the mirror structure, the drive to oscillate the mirror structure, the photodetector, and the associated signal processing and decoding circuitry all add size and weight to the scanner. In applications involving protracted use, a large heavy hand-held scanner can produce user fatigue. When use of the scanner produces fatigue or is in some other way inconvenient, the user is reluctant to operate the scanner. Any reluctance to consistently use the scanner defeats the data gathering purposes for which such bar code systems are intended. Also, a need exists for compact scanners to fit into small compact devices, such as notebooks.
Thus, an ongoing objective of bar code reader development is to miniaturize the reader as much as possible, and a need still exists to further reduce the size and weight of the scan engine and to provide a particularly convenient to use scanner. The mass of the moving components should be as low as possible to minimize the power required to produce the scanning movement.
It is also desirable to modularize the scan engine so that a particular module can be used in a variety of different scanners. A need exists, however, to develop a particularly compact, lightweight module which contains all the necessary scanner components.
It is an object of the present invention to reduce the size and weight of components used to produce scanning motion of the light beam, and to collect the reflected light.
A related object is to develop an electro-optical scanning system which is both smaller and lighter in weight.
It is yet a further object to produce a module which may be manufactured conveniently, and at low cost. A related object is to provide a module which may be assembled easily.
Briefly, and in general terms, the present invention provides an optical scan module including a base; a light source supported by the base, for generating and directing a light beam along a first segment of a first optical path to a symbol to be read; an optical assembly including a light-collecting portion for collecting and re-directing the reflected light along a second optical path, having an optical axis that is displaced from said first segment of the first optical path; a scan assembly including a reciprocally oscillatable scan mirror mounted for oscillating movement, and operative for receiving the light beam transmitted on the first segment of the first optical path, and for directing the light beam along a second segment of the first optical path through the window and exteriorly of the housing module; and a sensor supported by the base for detecting the collected reflected light that has been re-directed by the light-collecting portion, and for generating an electrical signal corresponding to the detected light intensity.
According to the invention there is further provided a bar code reader having a housing with a window, including an optical scan module having mounted thereon:
a) a light source for emitting a light beam;
b) a scanning assembly for receiving said light beam and for generating therefrom a scanning beam directed to the bar code symbol to be scanned so that the emitted scanning beam is substantially orthogonal to the window of the reader.
According to the invention there is further provided a small-size optical scan module in the form factor of a substantially rectangular parallelepiped module having dimensions approximately 20.6 mmxc3x9714.2 mmxc3x9711.4 mm. In the first embodiment, on one of the smaller sides (i.e. preferably a peripheral side 20.6 mmxc3x9711.4 mm or possibly also the side 14.2 mmxc3x9711.4 mm in dimension), there is mounted thereon a light source for emitting a light beam, a scanning assembly for receiving said light beam and for generating therefrom a scanning beam directed to an indicia to be read, a detector, and collector mirror arranged to received reflected light and to direct it to said detector.
In a second embodiment, in the same form factor, the light source is mounted on a first one of the peripheral sides (i.e. a 10.4 mmxc3x9720.6 mm side), the scanning assembly is mounted on a first base side (i.e. the 20.6 mmxc3x9714.2 mm side), the collection mirror is mounted on one of the base sides, and the detector mounted on one of the base sides. In such embodiment one or both of the base sides may be formed from a printed circuit board, while the peripheral side on which the light source is mounted forms part of an integral metal or plastic chassis of the module.
In a third embodiment, in the same form factor, the light source is mounted on a first one of the peripheral sides (i.e. a 20.6 mmxc3x9714.2 mm side), the scanning assembly is mounted on the second base side (i.e. the other 20.6 mmxc3x9714.2 mm side), the collection mirror is mounted on the first or second base side, and the detector mounted on the first or second base. In such embodiment the second base side is formed from a printed circuit.
In the preferred form of the second embodiment, the scanning assembly and the detector are mounted on the same base side, and the collection mirror is mounted on the opposite base side. Such an arrangement allows the components with electrical connections to be mounted on the printed circuit base side, while the critical optical components (the laser and collection mirror) are positioned in an integral chassis which forms the other base side and at least one of the peripheral sides.
In a fourth embodiment, in the same form factor, all the components are mounted on a first one of the base sides (i.e. a 10.4 mmxc3x9720.6 mm side), which is formed from a printed circuit board.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. Further features of the invention are set out in the appended independent claims, and further preferred features are set out in the dependent claims.